Automatic Headlamp Levelling for Xenon Headlamps
LIGHTING
DESCRIPTION AND OPERATION 86-2-29
Rear Fog Lamps
The rear fog lamps are only active with the ignition switch in position II. With the light control switch in the side lamp
position, the rear fog lamps can only be selected on when the front fog lamps are active. If the front fog lamps are
subsequently switched off, the rear fog lamps are automatically deselected.
With the light control switch in the headlamp position, the rear fog lamps can be activated individually, irrespective of
the front fog lamp status.
Brake Lamps
The brake lamps are active with the ignition switch in positions I or II. The LCM receives an input from the brake switch
which is used as a signal to activate the brake lamps. When HDC is active, the ABS ECU outputs a signal on a
separate hardwired connection to the LCM to activate the brake lamps when the HDC function is operating.
Reverse Lamps
The reverse lamps will operate with the ignition switch in position II. The LCM activate the reverse lamps on receipt
of an message on the I Bus that reverse gear has been engaged.
Main Beam/Direction Indicator Column Control Switch
Moving the switch rearwards, towards the driver, completes a ground path to the LCM. The ground path is completed
through a 1.2k
Ω
resistor which is sensed by the LCM. On receipt of this signal, the LCM activates the main beam
headlamps for as long as the switch is operated. This position is non-latching and operates with the ignition switch in
position I, but without the side lamps or headlamps being switched on.
Moving the switch forwards, into a latching position, completes a ground path to the LCM. The ground path is
completed through a 300
Ω
resistor which is sensed by the LCM. On receipt of this signal, the LCM activates the main
beam headlamps. The main beam will remain active until the switch is moved rearwards again, removing the ground
path. This function only operates when headlamps are selected on with the light control switch and the ignition switch
is in position II.
Moving the switch upwards or downwards completes a ground path to the LCM. The ground path is completed
through a 1.2k
Ω
resistor for the RH direction indicator or through a 300
Ω
resistor for the LH direction indicators which
is sensed by the LCM. On receipt of this signal the LCM activates the RH or LH direction indicators. The switch is a
latching switch, although the direction indicators can also be operated by lightly pushing the switch without engaging
the latch. The direction indicators will remain active until the switch is moved to the central off position. The direction
indicators operate with the ignition switch in position I.
With the ignition switched off, this switch position also operates the selected side parking lamps. Refer to 'Parking
Lamps' operation earlier in this section for details.
Automatic Headlamp Levelling (Xenon headlamps only)
The automatic headlamp levelling is only used on vehicle fitted with xenon headlamps. When the LCM detects that
the ignition is in position II and the side lamps or headlamps have been selected on using the light control switch, the
headlamp levelling control is activated. The headlamp levelling control is also activated when the LCM receives an
'engine running' signal on the I Bus, irrespective of the light control switch position.
When initially activated, the automatic headlamp levelling ECU cycles the stepper motors through their full range of
adjustment and stops at a default position. The ECU monitors the air suspension height sensor signals to determine
the vehicle angle and adjusts the headlamps accordingly. As the vehicle is driven, the ECU continuously monitors the
signals from the front and rear RH level sensors and also uses the speed and brake signals to determine the
operation. The ECU filters rapid changes of signals from the height sensors to prevent unnecessary adjustment.